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FreeBSD-SA-15:18.bsdpatch                                   Security Advisory
                                                          The FreeBSD Project

Topic:          shell injection vulnerability in patch(1)

Category:       contrib
Module:         patch
Announced:      2015-08-05
Credits:        Martin Natano
Affects:        FreeBSD 10.x.
Corrected:      2015-08-05 22:05:02 UTC (stable/10, 10.2-PRERELEASE)
                2015-08-05 22:05:02 UTC (stable/10, 10.2-BETA2-p3)
                2015-08-05 22:05:12 UTC (releng/10.2, 10.2-RC1-p2)
                2015-08-05 22:05:12 UTC (releng/10.2, 10.2-RC2-p1)
                2015-08-05 22:05:18 UTC (releng/10.1, 10.1-RELEASE-p17)
CVE Name:       CVE-2015-1418

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

The patch(1) utility takes a patch file produced by the diff(1) program and
apply the differences to an original file, producing a patched version.

The patch(1) utility supports patches that uses ed(1) script format, as
required by the POSIX.1-2008 standard.

ed(1) is a line-oriented text editor.

II.  Problem Description

Due to insufficient sanitization of the input patch stream, it is possible
for a patch file to cause patch(1) to pass certain ed(1) scripts to the
ed(1) editor, which would run commands.

III. Impact

This issue could be exploited to execute arbitrary commands as the user
invoking patch(1) against a specically crafted patch file, which could be
leveraged to obtain elevated privileges.

IV.  Workaround

No workaround is available, but systems where a privileged user does not
make use of patches without proper validation are not affected.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date.

A reboot is not required after updating.

2) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the i386 or amd64
platforms can be updated via the freebsd-update(8) utility:

# freebsd-update fetch
# freebsd-update install

A reboot is not required after updating.

3) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/SA-15:18/bsdpatch.patch
# fetch https://security.FreeBSD.org/patches/SA-15:18/bsdpatch.patch.asc
# gpg --verify bsdpatch.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile the operating system using buildworld and installworld as
described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

VI.  Correction details

The following list contains the correction revision numbers for each
affected branch.

Branch/path                                                      Revision
- -------------------------------------------------------------------------
stable/10/                                                        r286348
releng/10.1/                                                      r286351
releng/10.2/                                                      r286350
- -------------------------------------------------------------------------

To see which files were modified by a particular revision, run the
following command, replacing NNNNNN with the revision number, on a
machine with Subversion installed:

# svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

Or visit the following URL, replacing NNNNNN with the revision number:

<URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-1418>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-15:18.bsdpatch.asc>
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